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docs: Update the "writing a backend" documentation

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The documentation on how a ClutterBackend and stage are implemented
is a wee bit out of date.
This commit is contained in:
Emmanuele Bassi 2009-11-18 15:06:37 +00:00
parent f8e4e67272
commit 44f926556d
1 changed files with 23 additions and 16 deletions
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HACKING.backends
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@ -93,6 +93,10 @@ can be overridden:
ClutterBackend::get_display_size ClutterBackend::get_display_size
-- Use this function to retrieve the size of the display. -- Use this function to retrieve the size of the display.
ClutterBackend::create_context
-- This function is used to create the drawing context to be used
by Clutter.
ClutterBackend::ensure_context ClutterBackend::ensure_context
-- This function is used to ensure that the backend drawing context -- This function is used to ensure that the backend drawing context
is made current for passed ClutterStage, using the backend-specific is made current for passed ClutterStage, using the backend-specific
@ -116,27 +120,37 @@ Implementing the stage
ClutterStage acts as a wrapper object relaying all the drawing operations ClutterStage acts as a wrapper object relaying all the drawing operations
to the actual implementation. The implementation of the stage can be any to the actual implementation. The implementation of the stage can be any
ClutterActor subclass, as long as it does not subclass ClutterStage and GObject subclass, as long as it implements the ClutterStageWindow interface.
it implements the ClutterStageWindow interface.
The ClutterStageWindow interface contains a set of virtual functions that The ClutterStageWindow interface contains a set of virtual functions that
should be overridden by backends that support a windowing system, like should be overridden by backends that support a windowing system, like
::set_title(), ::set_fullscreen(), ::set_cursor_visible(), etc. ::set_title(), ::set_fullscreen(), ::set_cursor_visible(), etc.
The stage implementation actor must implement at least the ::realize and The stage implementation actor must implement:
::unrealize ClutterActor virtual functions. Inside the ::realize function
the stage implementation should: • ClutterStageWindow::get_wrapper()
• ClutterStageWindow::realize() and ::unrealize()
• ClutterStageWindow::show() and ::hide()
• ClutterStageWindow::resize()
• ClutterStageWindow::get_geometry()
The ::get_wrapper() implementation should return the pointer to the
ClutterStage actor using the ClutterStageWindow implementation.
In the ::realize virtual function the stage implementation should:
- create a new native window handle - create a new native window handle
- if the backend doesn't have a drawing context (either GL or GLES), - if the backend doesn't have a drawing context (either GL or GLES),
create one and pass it to the backend create one and pass it to the backend
In case of failure, the CLUTTER_ACTOR_REALIZED flag should be unset on The return value should be TRUE if the stage implementation was successfully
the stage implementation. realized, and FALSE otherwise.
Inside the ::unrealize function the stage implementation should: Inside the ::unrealize function the stage implementation should destroy
the native window handle created in ::realize().
- destroy the native window handle The ::resize() virtual function implementation should cause an update
of the COGL viewport.
NOTES NOTES
===== =====
@ -144,10 +158,3 @@ NOTES
If the platform is using X11 you should probably subclass ClutterBackendX11 If the platform is using X11 you should probably subclass ClutterBackendX11
and ClutterStageX11, which will provide you with a ready to use code and ClutterStageX11, which will provide you with a ready to use code
implementation for event handling and window management. implementation for event handling and window management.
Usual points of failure for backends are:
- calling public API, like clutter_actor_paint(), or checking properties
on the stage implementation instead of the ClutterStage wrapper.
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